Standby state maintaining device

ABSTRACT

A standby state maintaining device includes a secondary battery provided separately from a vehicle battery, a temperature sensor for the secondary battery, and a controller having a first operation mode of, in a state in which a starting switch of a vehicle is off, maintaining a power saving standby state of a vehicle-mounted information apparatus by selectively using either the secondary battery or the vehicle battery in accordance with a detected value provided by the temperature sensor.

TECHNICAL FIELD

The present invention relates to a standby state maintaining device fora vehicle-mounted information apparatus.

BACKGROUND ART

Conventionally, a vehicle-mounted information apparatus that performsthe functions of car navigation, display audio, or the like is mountedin a vehicle. Usually, a vehicle-mounted information apparatus mountedin a gasoline automobile operates with power supplied from a battery forstartup mounted in the automobile. Further, a vehicle-mountedinformation apparatus mounted in an electric automobile operates withpower supplied from an auxiliary battery mounted in the automobile (forexample, refer to Patent Literature 1).

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2013-225968

SUMMARY OF INVENTION Technical Problem

Conventionally, in an information apparatus other than a vehicle-mountedinformation apparatus, a standby state (referred to as a “power savingstandby state” hereafter) in which the power consumption is less thanthat in a state in which the information apparatus is operating(referred to as an “operating state” hereafter), and in which the timerequired for restart is shorter than that in a state in which the powersupply of the information apparatus is completely switched off (referredto as a “shutdown state” hereafter) is adopted. Concretely, for example,a power saving standby state corresponding to the status of S1, S2, orS3 in ACPI (Advanced Configuration and Power Interface) is adopted. Thispower saving standby state is one in which the information apparatusstands by in a state in which data in a volatile memory is held, bymaintaining the passage of a current to the memory, and in which acurrent (so-called “dark current”) is continuously consumed duringstandby. This power saving standby state is called “standby mode”,“sleep mode”, “suspend mode”, or the like.

In a vehicle-mounted information apparatus, it is difficult to adopt apower saving standby state from the viewpoint of avoiding a decrease inthe charge capacity of either a battery for startup or an auxiliarybattery (generically referred to as a “vehicle battery” hereafter) dueto a dark current in a state in which an ignition switch or a starterswitch (generically referred to as a “starting switch” hereafter) isoff. Therefore, a problem is that when the starting switch is switchedoff, the vehicle-mounted information apparatus has to be brought into ashutdown state, and the time required for restart at the time that thestarting switch is switched on the next time is long.

For this problem, it is possible to suppress the decrease in the chargecapacity of the vehicle battery while adopting the power saving standbystate in the vehicle-mounted information apparatus, by providing asecondary battery, such as a lithium ion battery or a nickel-metalhydride battery, separately from the vehicle battery, and causing thissecondary battery to supply a dark current. However, such a secondarybattery has a property of, when the secondary battery is charged anddischarged in a high temperature environment, decreasing its batterylife. Because the operating environment of the vehicle-mountedinformation apparatus is generally a high-temperature one, a problem isthat in a case in which such a secondary battery is simply provided inthe vehicle-mounted information apparatus, the battery life decreasesdue to charge and discharge in a high temperature environment.

The present invention is made in order to solve the above-mentionedproblems, and it is therefore an object of the present invention toprovide a technique for shortening the time required to start avehicle-mounted information apparatus by adopting a power saving standbystate, and increasing the life of a secondary battery for this powersaving standby state.

Solution to Problem

A standby state maintaining device of the present invention includes: asecondary battery disposed separately from a vehicle battery; atemperature sensor for the secondary battery; and a controller having afirst operation mode of, in a state in which a starting switch of avehicle is off, maintaining a power saving standby state of avehicle-mounted information apparatus by selectively using either thesecondary battery or the vehicle battery in accordance with a detectedvalue provided by the temperature sensor.

Advantageous Effects of Invention

According to the present invention, because the configuration isprovided as mentioned above, the time required to start thevehicle-mounted information apparatus can be shortened by virtue of theadoption of the power saving standby state, and the life of thesecondary battery for this power saving standby state can be increased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory drawing showing a main part of a standby statemaintaining device according to Embodiment 1 of the present invention;

FIG. 2 is a hardware block diagram showing a main part of an informationprocessing unit which a vehicle-mounted information apparatus accordingto Embodiment 1 of the present invention has;

FIG. 3A is a flowchart showing an operation of the standby statemaintaining device according to Embodiment 1 of the present invention;

FIG. 3B is a flowchart showing an operation of the standby statemaintaining device according to Embodiment 1 of the present invention;

FIG. 3C is a flowchart showing an operation of the standby statemaintaining device according to Embodiment 1 of the present invention;

FIG. 4 is an explanatory drawing showing a main part of another standbystate maintaining device according to Embodiment 1 of the presentinvention;

FIG. 5 is an explanatory drawing showing a main part of another standbystate maintaining device according to Embodiment 1 of the presentinvention;

FIG. 6 is an explanatory drawing showing a main part of a standby statemaintaining device according to Embodiment 2 of the present invention;

FIG. 7 is a flowchart showing an operation of the standby statemaintaining device according to Embodiment 2 of the present invention;

FIG. 8 is an explanatory drawing showing a main part of a standby statemaintaining device according to Embodiment 3 of the present invention;

FIG. 9 is a flowchart showing an operation of the standby statemaintaining device according to Embodiment 3 of the present invention;

FIG. 10 is an explanatory drawing showing a main part of a standby statemaintaining device according to Embodiment 4 of the present invention;

FIG. 11 is a flowchart showing an operation of the standby statemaintaining device according to Embodiment 4 of the present invention;

FIG. 12 is a flowchart showing another operation of the standby statemaintaining device according to Embodiment 4 of the present invention;and

FIG. 13 is a flowchart showing another operation of the standby statemaintaining device according to Embodiment 4 of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereafter, in order to explain this invention in greater detail,embodiments of the present invention will be described with reference tothe accompanying drawings.

Embodiment 1

FIG. 1 is an explanatory drawing showing a main part of a standby statemaintaining device according to Embodiment 1 of the present invention.FIG. 2 is a hardware block diagram showing a main part of an informationprocessing unit which a vehicle-mounted information apparatus accordingto Embodiment 1 of the present invention has. By referring to FIGS. 1and 2, the standby state maintaining device 100 of Embodiment 1 will beexplained.

As shown in FIG. 1, a vehicle 1 has a vehicle battery and a startingswitch 3. The vehicle battery 2 is comprised of, for example, a batteryfor startup in a case in which the vehicle 1 is a gasoline automobile,or an auxiliary battery in a case in which the vehicle 1 is an electricautomobile. The starting switch 3 is comprised of, for example, anignition switch in the case in which the vehicle 1 is a gasolineautomobile, or a starter switch in the case in which the vehicle 1 is anelectric automobile. As the starting switch 3, a request for start viacommunications is also included.

Further, the vehicle 1 has a vehicle-mounted information apparatus 4 anda display device 5. The vehicle-mounted information apparatus 4 iscomprised of, for example, an information apparatus for exclusive usewhich is provided integrally with the dashboard of the vehicle 1. Thevehicle-mounted information apparatus 4 performs, for example, thefunctions of either car navigation or display audio. The display device5 is comprised of, for example, a liquid crystal display or an organicEL (Electro Luminescence) display which is provided integrally with thevehicle-mounted information apparatus 4. The display device 5 displaysan image corresponding to image data outputted by the vehicle-mountedinformation apparatus 4. Concretely, for example, the display device 5displays an image showing information about a travel route currentlybeing guided using the car navigation, an image showing informationabout a piece of music currently being played back using the displayaudio, or the like.

Hereafter, a main part of the vehicle-mounted information apparatus 4will be explained.

An information processing unit 11 implements main functions in thevehicle-mounted information apparatus 4, i.e., the functions of eitherthe car navigation or the display audio. As shown in FIG. 2, theinformation processing unit 11 is comprised of a computer, and has aprocessor 21, a first memory 22, and a second memory 23.

The processor 21 is comprised of, for example, a CPU (Central ProcessingUnit) and a microcontroller (referred to as a “microcomputer”hereafter). The first memory 22 is comprised of, for example, a volatilememory such as a RAM (Random access memory). The second memory 23 iscomprised of, for example, a nonvolatile memory such as a ROM (Read OnlyMemory), an HDD (Hard Disk Drive), or an SSD (Solid State Drive).

A program for causing the computer to function as either the carnavigation or the display audio is stored in the second memory 23. Thefunctions of either the car navigation or the display audio areimplemented by the processor 21's reading and execution of the programstored in the second memory 23. The first memory 22 stores various dataused for processes performed by the program.

The information processing unit 11 freely switches among an operatingstate, a shutdown state, and a power saving standby state, in accordancewith an instruction from the microcomputer 18. The power saving standbystate of the information processing unit 11 is, for example, one inwhich the information processing unit stands by in a state in which datain the first memory 22 is held with the passage of a current to thefirst memory 22.

A power supply unit 12 supplies power to the information processing unit11 by using power supplied from either the vehicle battery 2 or asecondary battery 13. The power supply unit 12 is comprised of, forexample, a DC-DC converter.

The secondary battery 13 is provided separately from the vehicle battery2. The secondary battery 13 is comprised of, for example, a lithium ionbattery or a nickel-metal hydride battery. The secondary battery 13 hasa function of outputting a voltage value corresponding to the chargecapacity of the secondary battery 13 to the microcomputer 18.

A temperature sensor 14 is used for the secondary battery 13.Concretely, for example, the temperature sensor 14 is providedintegrally with the secondary battery 13, and detects the temperature ofthe main body of the secondary battery 13. As an alternative, forexample, the temperature sensor 14 is disposed adjacent to the secondarybattery 13, and detects the ambient temperature of the secondary battery13. The temperature sensor 14 outputs the value (referred to as the“detected value” hereafter) of the temperature detected thereby to themicrocomputer 18.

A switching circuit 15 is provided among the vehicle battery 2, thesecondary battery 13, and the power supply unit 12. The switchingcircuit 15 has one or more not-illustrated switches, and freely switchesthe turning on/off of an electric connection between the vehicle battery2 and the power supply unit 12, the turning on/off of an electricconnection between the secondary battery 13 and the power supply unit12, and the turning on/off of an electric connection between the vehiclebattery 2 and the secondary battery 13. The turning on/off of each ofthe switches is controlled by the microcomputer 18.

A charge and discharge control circuit 16 controls the charge anddischarge of the secondary battery 13 by switching the turning on/off ofa switching element 17 provided between the secondary battery 13 and theswitching circuit 15 in accordance with an instruction from themicrocomputer 18. The switching element 17 is comprised of, for example,an FET (Field Effect Transistor).

A range (referred to as a “reference range” hereafter) of values whichis an object to be compared with the detected value provided by thetemperature sensor 14 is set to the microcomputer 18 in advance. As thereference range, for example, a range in which an upper limit is set,but no lower limit is set, i.e., a range including values equal to orless than a predetermined threshold (referred to as a “first threshold”hereafter, e.g., +60° C.) is set up. Further, a value (referred to as a“reference capacity” hereafter, e.g., a value of 5% of the chargecapacity in a state in which the secondary battery 13 is fully charged)which is an object to be compared with the charge capacity of thesecondary battery 13 is set to the microcomputer 18 in advance. Inaddition, a value (referred to as a “first reference time” hereafter,e.g., 30 minutes) which is an object to be compared with the duration ofthe power saving standby state using the vehicle battery 2 is set to themicrocomputer 18 in advance.

The microcomputer 18 has an operation mode (referred to as a “firstoperation mode” hereafter) of, in a state in which the starting switch 3is off, maintaining the power saving standby state of the informationprocessing unit 11 by selectively using either the secondary battery 13or the vehicle battery 2 in accordance with the detected value of thetemperature sensor 14. More concretely, in the first operation mode, themicrocomputer 18 maintains the power saving standby state by using thesecondary battery 13 when the detected value of the temperature sensor14 is within the reference range, whereas the microcomputer maintainsthe power saving standby state by using the vehicle battery 2 when thedetected value of the temperature sensor 14 is outside the referencerange. The details of the operation of the microcomputer 18 in the firstoperation mode will be mentioned later by reference to a flowchart ofFIG. 3.

Further, in a state in which the starting switch 3 is on, themicrocomputer 18 sets the electric connection in the switching circuit15 between the vehicle battery 2 and the power supply unit 12 to the onstate. As a result, the power supply unit 12 supplies power to theinformation processing unit 11 by using the power supplied from thevehicle battery 2.

Further, in the state in which the starting switch 3 is on, themicrocomputer 18 sets the electric connection in the switching circuit15 between the vehicle battery 2 and the secondary battery 13 to the onstate, and also instructs the charge and discharge control circuit 16 tocharge the secondary battery 13. As a result, the secondary battery 13is charged.

A control unit 19 is comprised of the switching circuit 15, the chargeand discharge control circuit 16, the switching element 17, and themicrocomputer 18. The standby state maintaining device 100 is comprisedof the secondary battery 13, the temperature sensor 14, and the controlunit 19. The vehicle-mounted information apparatus 4 is comprised of theinformation processing unit 11, the power supply unit 12, and thestandby state maintaining device 100.

Next, operations of the standby state maintaining device 100 will beexplained by reference to the flowchart of FIG. 3, focusing on anoperation in the first operation mode which is performed by themicrocomputer 18. In an initial state, the starting switch 3 is in theon state, the power supply unit 12 supplies power to the informationprocessing unit 11 by using the power supplied from the vehicle battery2, and the information processing unit 11 is in the operating state.Further, the secondary battery 13 is in a state in which a charge iscompleted.

More specifically, the electric connection in the switching circuit 15between the vehicle battery 2 and the power supply unit 12 is in the onstate, the electric connection between the secondary battery 13 and thepower supply unit 12 is in the off state, and the electric connectionbetween the vehicle battery 2 and the secondary battery 13 is in the offstate. Further, the switching element 17 is in the off state. When thestarting switch 3 is switched from the on state to the off state, themicrocomputer 18 starts a process of step ST1.

First, the microcomputer 18, in step ST1, acquires the detected value ofthe temperature sensor 14 from the temperature sensor 14. Then, themicrocomputer 18, in step ST2, determines whether or not the detectedvalue acquired in step ST1 is within the reference range.

When the detected value acquired in step ST1 is within the referencerange (“YES” in step ST2), the microcomputer 18, in step ST3, starts thepower saving standby state using the secondary battery 13. Morespecifically, the microcomputer 18 switches the electric connection inthe switching circuit 15 between the vehicle battery 2 and the powersupply unit 12 from the on state to the off state, and also switches theelectric connection between the secondary battery 13 and the powersupply unit 12 from the off state to the on state. Further, themicrocomputer 18 instructs the charge and discharge control circuit 16to start discharging the secondary battery 13. In addition, themicrocomputer 18 instructs the information processing unit 11 to switchfrom the operating state to the power saving standby state.

In contrast, when the detected value acquired in step ST1 is outside thereference range (“NO” in step ST2), the microcomputer 18, in step ST4,starts the power saving standby state using the vehicle battery 2. Morespecifically, the microcomputer 18 instructs the information processingunit 11 to switch from the operating state to the power saving standbystate.

After step ST3, the microcomputer 18, in step ST11, acquires thedetected value of the temperature sensor 14 from the temperature sensor14. Then, the microcomputer 18, in step ST12, determines whether or notthe detected value acquired in step ST11 is within the reference range.

When the detected value acquired in step ST11 is within the referencerange (“YES” in step ST12), the microcomputer 18, in step ST13, acquiresthe voltage value corresponding to the charge capacity of the secondarybattery 13 from the secondary battery 13. Then, the microcomputer 18, instep ST14, determines whether or not the charge capacity of thesecondary battery 13 is equal to or greater than the reference capacityby using the voltage value acquired in step ST13.

When the charge capacity of the secondary battery 13 is equal to orgreater than the reference capacity (“YES” in step ST14), themicrocomputer 18 returns to the process of step ST11 while continuingthe power saving standby state using the secondary battery 13 (stepST15).

In contrast, when the charge capacity of the secondary battery 13 isless than the reference capacity (“NO” in step ST14), the microcomputer18, in step ST16, ends the power saving standby state. Morespecifically, the microcomputer 18 switches the electric connection inthe switching circuit 15 between the secondary battery 13 and the powersupply unit 12 from the on state to the off state. Further, themicrocomputer 18 instructs the charge and discharge control circuit 16to end the discharge of the secondary battery 13. In addition, themicrocomputer 18 instructs the information processing unit 11 to switchfrom the power saving standby state to the shutdown state.

Further, when the detected value acquired in step ST11 is outside thereference range (“NO” in step ST12), the microcomputer 18, in step ST17,switches from the power saving standby state using the secondary battery13 to the power saving standby state using the vehicle battery 2. Morespecifically, the microcomputer 18 switches the electric connection inthe switching circuit 15 between the vehicle battery 2 and the powersupply unit 12 from the off state to the on state, and also switches theelectric connection between the secondary battery 13 and the powersupply unit from the on state to the off state. Further, themicrocomputer 18 instructs the charge and discharge control circuit 16to end the discharge of the secondary battery 13.

After step ST4 or ST17, the microcomputer 18, in step ST21, calculatesthe duration of the power saving standby state using the vehicle battery2. More concretely, the microcomputer 18 calculates the cumulative sumof durations of the power saving standby state using the vehicle battery2 which occur after the starting switch 3 has been switched off. Then,the microcomputer 18, in step ST22, compares the duration calculated instep ST21 with the first reference time.

When the duration calculated in step ST21 is equal to or less than thefirst reference time (“NO” in step ST22), the microcomputer 18, in stepST23, acquires the detected value of the temperature sensor 14 from thetemperature sensor 14. Then, the microcomputer 18, in step ST24,determines whether or not the detected value acquired in step ST23 iswithin the reference range.

When the detected value acquired in step ST23 is outside the referencerange (“NO” in step ST24), the microcomputer 18 returns to the processof step ST21 while continuing the power saving standby state using thevehicle battery 2 (step ST25).

In contrast, when the detected value acquired in step ST23 is within thereference range (“YES” in step ST24), the microcomputer 18, in stepST26, switches from the power saving standby state using the vehiclebattery 2 to the power saving standby state using the secondary battery13. More specifically, the microcomputer 18 switches the electricconnection in the switching circuit 15 between the vehicle battery 2 andthe power supply unit 12 from the on state to the off state, and alsoswitches the electric connection between the secondary battery 13 andthe power supply unit from the off state to the on state. Further, themicrocomputer 18 instructs the charge and discharge control circuit 16to start discharging the secondary battery 13. After step ST26, themicrocomputer 18 advances to the process of step ST11.

Further, when the duration calculated in step ST21 exceeds the firstreference time (“YES” in step ST22), the microcomputer 18, in step ST27,ends the power saving standby state. More specifically, themicrocomputer 18 switches the electric connection in the switchingcircuit 15 between the vehicle battery 2 and the power supply unit 12from the on state to the off state. Further, the microcomputer 18instructs the information processing unit 11 to switch from the powersaving standby state to the shutdown state.

In this way, in the state in which the starting switch 3 is off, thestandby state maintaining device 100 of Embodiment 1 maintains the powersaving standby state of the information processing unit 11 byselectively using either the secondary battery 13 or the vehicle battery2 in accordance with the detected value of the temperature sensor 14. Byvirtue of the adoption of the power saving standby state, the timerequired to start the vehicle-mounted information apparatus 4 at thetime that the starting switch 3 is switched on can be shortened.Further, by maintaining the power saving standby state by selectivelyusing either the secondary battery 13 or the vehicle battery 2 inaccordance with the detected value of the temperature sensor 14, thedecrease in the charge capacity of the vehicle battery 2 due to a darkcurrent in the state in which the starting switch 3 is off can besuppressed, and the life of the secondary battery 13 can be increased.

More concretely, the standby state maintaining device 100 maintains thepower saving standby state by using the secondary battery 13 when thedetected value of the temperature sensor 14 is within the referencerange (steps ST11 to ST15), whereas the standby state maintaining devicemaintains the power saving standby state by using the vehicle battery 2when the detected value of the temperature sensor 14 is outside thereference range (steps ST21 to ST25). By setting the upper limit on thereference range, i.e., the first threshold to an appropriate value, thesecondary battery 13 can be prevented from being discharged in a hightemperature environment. As a result, the decrease in the battery lifeof the secondary battery 13 due to the discharge can be prevented.

The functions implemented by the information processing unit 11 are notlimited to those of either the car navigation or the display audio. Theinformation processing unit 11 can implement any function in thevehicle-mounted information apparatus 4.

Further, the power saving standby state of the information processingunit 11 can be one in which the information processing unit stands by ina state in which the passage of a current to the CPU of the processor21, in addition to the passage of a current to the first memory 22, isheld. As a result, the time required to start the vehicle-mountedinformation apparatus 4 at the time that the starting switch 3 isswitched on can be further shortened.

Further, the microcomputer 18 can be constituted integrally with themicrocomputer of the processor 21. As a result, the number ofmicrocomputers in the vehicle-mounted information apparatus 4 can bereduced.

Further, the value of the first threshold is not limited to +60° C. Thefirst threshold can be set to any value in accordance with the heatresistance of the secondary battery 13, a characteristic showing theamount of decrease for temperature of the battery life, the decreasebeing caused by charge and discharge.

Further, the value of the first reference time is not limited to 30minutes. The first reference time can be set to any value in accordancewith the capacity of the vehicle battery 2, the magnitude of the darkcurrent consumed by the information processing unit 11.

Further, the value of the reference capacity is not limited to 5% of thecharge capacity in the state in which the secondary battery 13 is fullycharged. The reference capacity can be set to any value in accordancewith the capacity of the secondary battery 13, the magnitude of the darkcurrent consumed by the information processing unit 11.

Further, as the reference range, a range in which an upper limit is setand a lower limit is set, i.e., a range including values equal to orgreater than a predetermined threshold (referred to as a “secondthreshold” hereafter, e.g., −20° C.) and equal to or less than the firstthreshold can be set up. The secondary battery 13 has, in addition tothe property of decreasing its battery life when charge and dischargeare performed in a high temperature environment, as mentioned above, theproperty of decreasing its battery life also when charge and dischargeare performed in a low temperature environment. By setting the lowerlimit on the reference range, i.e., the second threshold to anappropriate value, the secondary battery 13 can be prevented from beingdischarged in a low temperature environment. As a result, the decreasein the battery life of the secondary battery 13 due to the discharge canbe prevented.

Further, the charge and discharge control circuit 16 can have anot-illustrated CPU. Further, the processes of steps ST13 and ST14 whichare shown in FIG. 3B can be performed by the CPU instead of themicrocomputer 18. An example of the standby state maintaining device 100in this case is shown in FIG. 4. The CPU in the charge and dischargecontrol circuit 16 acquires the voltage value corresponding to thecharge capacity of the secondary battery 13 from the secondary battery13 in accordance with an instruction from the microcomputer 18 (stepST13). Then, the CPU in the charge and discharge control circuit 16determines whether or not the charge capacity of the secondary battery13 is equal to or greater than the reference capacity by using thevoltage value acquired in step ST13 (step ST14). The CPU in the chargeand discharge control circuit 16 outputs a result of the determinationto the microcomputer 18.

Further, some of the components of the standby state maintaining device100 can be provided outside the vehicle-mounted information apparatus 4.An example of the standby state maintaining device 100 in this case isshown in FIG. 5. As shown in FIG. 5, a secondary battery module 6 isprovided outside the vehicle-mounted information apparatus 4. Thevehicle-mounted information apparatus 4 and the secondary battery module6 are connected to each other in such a way that power supply isperformed freely between them via an electric supply line, and in such away that communications are performed freely between them via a controlline. The secondary battery 13, the temperature sensor 14, and theswitching element 17 in the standby state maintaining device 100 areprovided in the secondary battery module 6. Further, a CPU 31 whichserves as the function of the charge and discharge control circuit 16shown in FIG. 1 is provided in the secondary battery module 6. Theprocessing shown in FIG. 3 is implemented by cooperation between themicrocomputer 18 provided in the vehicle-mounted information apparatus 4and the CPU 31 provided in the secondary battery module 6.

As mentioned above, the standby state maintaining device 100 ofEmbodiment 1 includes the secondary battery 13 provided separately fromthe vehicle battery 2, the temperature sensor 14 for the secondarybattery 13, and the control unit 19 having the first operation mode of,in the state in which the starting switch 3 of the vehicle 1 is off,maintaining the power saving standby state of the vehicle-mountedinformation apparatus 4 by selectively using either the secondarybattery 13 or the vehicle battery 2 in accordance with the detectedvalue of the temperature sensor 14. By virtue of the adoption of thepower saving standby state, the time required to start thevehicle-mounted information apparatus 4 at the time that the startingswitch 3 is switched on can be shortened. Further, by maintaining thepower saving standby state by selectively using either the secondarybattery 13 or the vehicle battery 2 in accordance with the detectedvalue of the temperature sensor 14, the decrease in the charge capacityof the vehicle battery 2 due to a dark current in the state in which thestarting switch 3 is off can be suppressed, and the life of thesecondary battery 13 can be increased.

Further, in the first operation mode, the control unit 19 maintains thepower saving standby state by using the secondary battery 13 when thedetected value is within the reference range (steps ST11 to ST15),whereas the control unit maintains the power saving standby state byusing the vehicle battery 2 when the detected value is outside thereference range (steps ST21 to ST25). By setting the reference range toan appropriate range, the secondary battery 13 can be prevented frombeing discharged in a high temperature environment or a low temperatureenvironment. As a result, the decrease in the battery life of thesecondary battery 13 due to the discharge can be prevented.

Further, when the detected value falls outside the reference range (“NO”in step ST12) while the power saving standby state is maintained usingthe secondary battery 13 in the first operation mode (steps ST11 toST15), the control unit 19 switches the states of the vehicle-mountedinformation apparatus 4 from the power saving standby state using thesecondary battery 13 to the power saving standby state using the vehiclebattery 2 (step ST17). As a result, the secondary battery 13 can beprevented more surely from being discharged in a high temperatureenvironment or a low temperature environment.

Further, when the charge capacity of the secondary battery 13 becomesless than the reference capacity (“NO” in step ST14) while the powersaving standby state is maintained using the secondary battery 13 in thefirst operation mode (steps ST11 to ST15), the control unit 19 ends thepower saving standby state (step ST16). By setting the referencecapacity to an appropriate value, the overdischarge of the secondarybattery 13 can be prevented.

Further, when the detected value falls within the reference range (“YES”in step ST24) while the power saving standby state is maintained usingthe vehicle battery 2 in the first operation mode (steps ST21 to ST25),the control unit 19 switches the states of the vehicle-mountedinformation apparatus 4 from the power saving standby state using thevehicle battery 2 to the power saving standby state using the secondarybattery 13 (step ST26). As a result, the decrease in the charge capacityof the vehicle battery 2 due to a dark current can be furthersuppressed.

Further, when the duration of the power saving standby state using thevehicle battery 2 exceeds the first reference time (“YES” in step ST22)while the power saving standby state is maintained using the vehiclebattery 2 in the first operation mode (steps ST21 to ST25), the controlunit 19 ends the power saving standby state (step ST27). As a result,the decrease in the charge capacity of the vehicle battery 2 due to adark current can be further suppressed.

Further, as the reference range, either a range including values equalto or less than the first threshold, or a range including values equalto or greater than the second threshold less than the first threshold,and equal to or less than the first threshold is set up. By setting thefirst threshold to an appropriate value, the secondary battery 13 can beprevented from being discharged in a high temperature environment.Further, by setting the second threshold to an appropriate value, thesecondary battery 13 can be prevented from being discharged in a lowtemperature environment.

Further, the secondary battery 13 is comprised of a lithium ion batteryor a nickel-metal hydride battery. In general, the amounts of decreaseof the battery lives of a lithium ion battery and a nickel-metal hydridebattery at the time that charge and discharge are performed in a hightemperature environment are greater than that of a nickel cadmiumbattery. Therefore, the battery life can be greatly improved by avoidingdischarge in a high temperature environment.

Embodiment 2

FIG. 6 is an explanatory drawing showing a main part of a standby statemaintaining device according to Embodiment 2 of the present invention.By referring to FIG. 6, the standby state maintaining device 100 a ofEmbodiment 2 will be explained. The same components as those of thestandby state maintaining device 100 of Embodiment 1 shown in FIG. 1 aredenoted by the same reference numerals, and an explanation of thecomponents will be omitted hereafter. Further, because the hardwareconfiguration of an information processing unit 11 is the same as thatexplained by reference to FIG. 2 in Embodiment 1, an illustration and anexplanation of the hardware configuration will be omitted hereafter.

A microcomputer 18 a has the same first operation mode as that of themicrocomputer 18 according to Embodiment 1. In addition to this mode,the microcomputer 18 a has an operation mode (referred to as a “secondoperation mode” hereafter) of, in a state in which a starting switch 3is off, maintaining a power saving standby state of the informationprocessing unit 11 by using a vehicle battery 2. The microcomputer 18 aperforms the second operation mode until a predetermined time (referredto as a “second reference time” hereafter, e.g., 30 minutes) elapsessince the starting switch 3 has been switched off, and performs thefirst operation mode after the second reference time elapses.

Further, in a state in which the starting switch 3 is on, themicrocomputer 18 a sets an electric connection in a switching circuit 15between the vehicle battery 2 and a power supply unit 12 to an on state,like the microcomputer 18 according to Embodiment 1. As a result, thepower supply unit 12 supplies power to the information processing unit11 by using power supplied from the vehicle battery 2.

Further, in the state in which the starting switch 3 is on, themicrocomputer 18 a sets an electric connection in the switching circuit15 between the vehicle battery 2 and a secondary battery 13 to an onstate, and also instructs a charge and discharge control circuit 16 tocharge the secondary battery 13, like the microcomputer 18 according toEmbodiment 1. As a result, the secondary battery 13 is charged.

A control unit 19 a is comprised of the switching circuit 15, the chargeand discharge control circuit 16, a switching element 17, and themicrocomputer 18 a. The standby state maintaining device 100 a iscomprised of the secondary battery 13, a temperature sensor 14, and thecontrol unit 19 a.

Next, operations of the standby state maintaining device 100 a will beexplained by reference to a flowchart of FIG. 7, focusing on operationsin the first operation mode and in the second operation mode which areperformed by the microcomputer 18 a. In an initial state, the startingswitch 3 is in the on state, the power supply unit 12 supplies power tothe information processing unit 11 by using the power supplied from thevehicle battery 2, and the information processing unit 11 is in anoperating state. Further, the secondary battery 13 is in a state inwhich a charge is completed.

More specifically, the electric connection in the switching circuit 15between the vehicle battery 2 and the power supply unit 12 is in the onstate, the electric connection between the secondary battery 13 and thepower supply unit 12 is in the off state, and the electric connectionbetween the vehicle battery 2 and the secondary battery 13 is in the offstate. Further, the switching element 17 is in the off state. When thestarting switch 3 is switched from the on state to the off state, themicrocomputer 18 a starts a process of step ST31.

First, in step ST31, the microcomputer 18 a starts the operation in thesecond operation mode. More specifically, the microcomputer 18 ainstructs the information processing unit 11 to switch from theoperating state to the power saving standby state.

Then, the microcomputer 18 a, in step ST32, calculates the time whichhas elapsed since the starting switch 3 has been switched off. Then, themicrocomputer 18 a, in step ST33, compares the elapsed time calculatedin step ST32 with the second reference time.

When the elapsed time calculated in step ST32 is equal to or less thanthe second reference time (“NO” in step ST33), the microcomputer 18 areturns to the process of step ST32 while continuing the operation inthe second operation mode (step ST34).

In contrast, when the elapsed time calculated in step ST32 exceeds thesecond reference time (“YES” in step ST33), the microcomputer 18 aperforms the first operation mode (step ST35). Concretely, for example,the microcomputer 18 a advances to the process of step ST23 shown inFIG. 3C.

For example, when the driver parks or stops a vehicle 1 for the purposeof shopping or fueling, there is a high probability that the parking orstopping will be ended in a short time. In such short-time parking orstopping, the decrease in the charge capacity of the vehicle battery 2due to a dark current is small even though the power saving standbystate of the information processing unit 11 is maintained using thevehicle battery 2.

Therefore, the standby state maintaining device 100 a of Embodiment 2performs the second operation mode to maintain the power saving standbystate of the information processing unit 11 by using the vehicle battery2 until the predetermined time, i.e., the second reference time elapsessince the starting switch 3 has been switched off. As a result, inshort-time parking or stopping, the secondary battery 13 can beprevented from being discharged. As a result, the number of times of thecharge and discharge of the secondary battery 13 can be reduced, and thelife of the secondary battery 13 can be further increased.

The value of the second reference time is not limited to 30 minutes. Thesecond reference time can be set to any value in accordance with thecapacity of the vehicle battery 2, the magnitude of the dark currentconsumed by the information processing unit 11. Further, the secondreference time can be the same as the first reference time, or can bedifferent from the first reference time.

Further, the standby state maintaining device 100 a of Embodiment 2 canadopt various variants which are the same as those explained inEmbodiment 1. For example, a part of the processing in the firstoperation mode can be performed by a CPU in the charge and dischargecontrol circuit 16, like in the case of the example shown in FIG. 4. Asan alternative, for example, the secondary battery 13, the temperaturesensor 14 can be provided outside the vehicle-mounted informationapparatus 4, like in the case of the example shown in FIG. 5.

As mentioned above, in the standby state maintaining device 100 a ofEmbodiment 2, the control unit 19 a has the second operation mode of, inthe state in which the starting switch 3 is off, maintaining the powersaving standby state by using the vehicle battery 2. By performing thesecond operation mode, the number of times of the charge and dischargeof the secondary battery 13 can be reduced, and the life of thesecondary battery 13 can be further increased.

Further, the control unit 19 a performs the second operation mode untilthe second reference time elapses since the starting switch 3 has beenswitched off (steps ST31 to ST34), and performs the first operation modeafter the second reference time elapses (step ST35). As a result, inshort-time parking or stopping, the secondary battery 13 can beprevented from being discharged. As a result, the number of times of thecharge and discharge of the secondary battery 13 can be reduced, and thelife of the secondary battery 13 can be further increased.

Embodiment 3

FIG. 8 is an explanatory drawing showing a main part of a standby statemaintaining device according to Embodiment 3 of the present invention.By referring to FIG. 8, the standby state maintaining device 100 b ofEmbodiment 3 will be explained. The same components as those of thestandby state maintaining device 100 of Embodiment 1 shown in FIG. 1 aredenoted by the same reference numerals, and an explanation of thecomponents will be omitted hereafter. Further, because the hardwareconfiguration of an information processing unit 11 is the same as thatexplained by reference to FIG. 2 in Embodiment 1, an illustration and anexplanation of the hardware configuration will be omitted hereafter.

The vehicle-mounted information apparatus 4 has a GPS (GlobalPositioning System) receiver 41. The GPS receiver 41 receives GPSsignals transmitted by not-illustrated GPS satellites by using a GPSantenna 7.

In Embodiment 3, an information processing unit 11 implements thefunctions of car navigation. More specifically, the informationprocessing unit 11 has a function of calculating the position of avehicle 1 by using the GPS signals received by the GPS receiver 41. Whena starting switch 3 is switched off, the information processing unit 11determines the type of a facility corresponding to the position of thevehicle 1 by using map data stored in a second memory 23. Theinformation processing unit 11 outputs information (referred to as“facility information” hereafter) showing the determined facility typeto a microcomputer 18 b.

The microcomputer 18 b has the same first and second operation modes asthose of the microcomputer 18 a according to Embodiment 2. Themicrocomputer 18 b acquires the facility information from theinformation processing unit 11 when the starting switch 3 is switchedoff. The microcomputer 18 b selectively performs either the firstoperation mode or the second operation mode in accordance with thefacility type shown by the facility information. Concretely, forexample, when the facility shown by the facility information is aparking lot of a gas station or store, the microcomputer 18 b performsthe second operation mode; otherwise, the microcomputer performs thefirst operation mode.

Further, in a state in which the starting switch 3 is on, themicrocomputer 18 b sets an electric connection in a switching circuit 15between a vehicle battery 2 and a power supply unit 12 to an on state,like the microcomputers 18 and 18 a according to Embodiments 1 and 2. Asa result, the power supply unit 12 supplies power to the informationprocessing unit 11 by using power supplied from the vehicle battery 2.

Further, in the state in which the starting switch 3 is on, themicrocomputer 18 b sets an electric connection in the switching circuit15 between the vehicle battery 2 and a secondary battery 13 to an onstate, and also instructs a charge and discharge control circuit 16 tocharge the secondary battery 13, like the microcomputers 18 and 18 aaccording to Embodiments 1 and 2. As a result, the secondary battery 13is charged.

A control unit 19 b is comprised of the switching circuit 15, the chargeand discharge control circuit 16, a switching element 17, and themicrocomputer 18 b. The standby state maintaining device 100 b iscomprised of the secondary battery 13, a temperature sensor 14, and thecontrol unit 19 b.

Next, operations of the standby state maintaining device 100 b will beexplained by reference to a flowchart of FIG. 9, focusing on operationsin the first operation mode and in the second operation mode which areperformed by the microcomputer 18 b. In an initial state, the startingswitch 3 is in the on state, the power supply unit 12 supplies power tothe information processing unit 11 by using the power supplied from thevehicle battery 2, and the information processing unit 11 is in anoperating state. Further, the secondary battery 13 is in a state inwhich a charge is completed. When the starting switch 3 is switched fromthe on state to the off state, the microcomputer 18 b starts a processof step ST41.

First, the microcomputer 18 b, in step ST41, acquires the facilityinformation from the information processing unit 11. This facilityinformation shows the type of a facility corresponding to the positionof the vehicle 1 at the time that the starting switch 3 is switched off.

Then, the microcomputer 18 b, in step ST42, selects either the firstoperation mode or the second operation mode in accordance with thefacility type shown by the facility information acquired in step ST41.Concretely, for example, when the facility shown by the facilityinformation is a parking lot of a gas station or store, themicrocomputer 18 b selects the second operation mode; otherwise, themicrocomputer selects the first operation mode.

Then, the microcomputer 18 b, in step ST43, performs the operation modeselected in step ST42.

When the vehicle 1 is parked or stopped in a parking lot of a gasstation or store, there is a high probability that the parking orstopping will be ended in a short time. In such short-time parking orstopping, the decrease in the charge capacity of the vehicle battery 2due to a dark current is small even though a power saving standby stateof the information processing unit 11 is maintained using the vehiclebattery 2.

Therefore, the standby state maintaining device 100 b of Embodiment 3performs the second operation mode to maintain the power saving standbystate of the information processing unit 11 by using the vehicle battery2 when a facility corresponding to the position of the vehicle 1 at thetime that the starting switch 3 is switched off is a parking lot of agas station or store. As a result, in short-time parking or stopping,the secondary battery 13 can be prevented from being discharged. As aresult, the number of times of the charge and discharge of the secondarybattery 13 can be reduced, and the life of the secondary battery 13 canbe further increased.

The criterion for the selection in step ST42 is not limited to whetheror not the facility shown by the facility information is a parking lotof a gas station or store. The standby state maintaining device 100 bshould just select the second operation mode when the facilityinformation shows a facility having a high probability that the parkingor stopping will be ended in a short time, or select the first operationmode otherwise.

Further, the standby state maintaining device 100 b of Embodiment 3 canadopt various variants which are the same as those explained inEmbodiment 1. For example, a part of the processing in the firstoperation mode can be performed by a CPU in the charge and dischargecontrol circuit 16, like in the case of the example shown in FIG. 4. Asan alternative, for example, the secondary battery 13, the temperaturesensor 14 can be provided outside the vehicle-mounted informationapparatus 4, like in the case of the example shown in FIG. 5.

As mentioned above, in the standby state maintaining device 100 b ofEmbodiment 3, the control unit 19 b has the second operation mode of, inthe state in which the starting switch 3 is off, maintaining the powersaving standby state by using the vehicle battery 2. By performing thesecond operation mode, the number of times of the charge and dischargeof the secondary battery 13 can be reduced, and the life of thesecondary battery 13 can be further increased.

Further, the control unit 19 b acquires information showing the type ofa facility corresponding to the position of the vehicle 1 when thestarting switch 3 is switched off (step ST41), and selectively performseither the first operation mode or the second operation mode inaccordance with the facility type (steps ST42 and ST43). As a result, inshort-time parking or stopping, the secondary battery 13 can beprevented from being discharged. As a result, the number of times of thecharge and discharge of the secondary battery 13 can be reduced, and thelife of the secondary battery 13 can be further increased.

Embodiment 4

FIG. 10 is an explanatory drawing showing a main part of a standby statemaintaining device according to Embodiment 4 of the present invention.By referring to FIG. 10, the standby state maintaining device 100 c ofEmbodiment 4 will be explained. The same components as those of thestandby state maintaining device 100 of Embodiment 1 shown in FIG. 1 aredenoted by the same reference numerals, and an explanation of thecomponents will be omitted hereafter. Further, because the hardwareconfiguration of an information processing unit 11 is the same as thatexplained by reference to FIG. 2 in Embodiment 1, an illustration and anexplanation of the hardware configuration will be omitted hereafter.

A microcomputer 18 c causes a cooling device 51 for a secondary battery13 to operate in a state in which a starting switch 3 is off. Thecooling device 51 is comprised of, for example, a cooling fan providedin the vehicle-mounted information apparatus 4. More concretely, themicrocomputer 18 c causes the cooling device 51 to operate at a timingshown in one of the following three concrete examples.

The first concrete example is one in which the cooling device 51 iscaused to operate until a detected value provided by a temperaturesensor 14 falls within a reference range after the starting switch 3 hasbeen switched off. In this case, the microcomputer 18 c has the samefirst and second operation modes as those of the microcomputers 18 a and18 b according to Embodiments 2 and 3. The microcomputer 18 c performsthe second operation mode until the detected value of the temperaturesensor 14 falls within the reference range after the starting switch 3has been switched off, and then performs the first operation mode.

The second concrete example is one in which the cooling device 51 iscaused to operate until a predetermined time (referred to as a “thirdreference time” hereafter, e.g., 30 minutes) elapses since the startingswitch 3 has been switched off. In this case, the microcomputer 18 c hasthe same first and second operation modes as those of the microcomputers18 a and 18 b according to Embodiments 2 and 3. The microcomputer 18 cperforms the second operation mode until the third reference timeelapses since the starting switch 3 has been switched off, and thenperforms the first operation mode.

The third concrete example is one in which the cooling device 51 iscaused to operate when the detected value of the temperature sensor 14is greater than a first threshold in the first operation mode. In thiscase, the microcomputer 18 c has the same first operation mode as thatof the microcomputer 18 according to Embodiment 1. The microcomputer 18c starts the operation in the first operation mode when the startingswitch 3 is switched off.

Further, in a state in which the starting switch 3 is on, themicrocomputer 18 c sets an electric connection in a switching circuit 15between a vehicle battery 2 and a power supply unit 12 to an on state,like the microcomputers 18, 18 a, and 18 b according to Embodiments 1 to3. As a result, the power supply unit 12 supplies power to theinformation processing unit 11 by using power supplied from the vehiclebattery 2.

Further, in the state in which the starting switch 3 is on, themicrocomputer 18 c sets an electric connection in the switching circuit15 between the vehicle battery 2 and a secondary battery 13 to an onstate, and also instructs a charge and discharge control circuit 16 tocharge the secondary battery 13, like the microcomputers 18, 18 a, and18 b according to Embodiments 1 to 3. As a result, the secondary battery13 is charged.

A control unit 19 c is comprised of the switching circuit 15, the chargeand discharge control circuit 16, a switching element 17, and themicrocomputer 18 c. The standby state maintaining device 100 c iscomprised of the secondary battery 13, the temperature sensor 14, andthe control unit 19 c.

Next, operations of the standby state maintaining device 100 c will beexplained by reference to a flowchart of FIG. 11, focusing on anoperation of the microcomputer 18 c in the above-mentioned firstconcrete example. In an initial state, the starting switch 3 is in theon state, the power supply unit 12 supplies power to the informationprocessing unit 11 by using the power supplied from the vehicle battery2, and the information processing unit 11 is in an operating state.Further, the secondary battery 13 is in a state in which a charge iscompleted.

More specifically, the electric connection in the switching circuit 15between the vehicle battery 2 and the power supply unit 12 is in the onstate, the electric connection between the secondary battery 13 and thepower supply unit 12 is in the off state, and the electric connectionbetween the vehicle battery 2 and the secondary battery 13 is in the offstate. Further, the switching element 17 is in the off state. When thestarting switch 3 is switched from the on state to the off state, themicrocomputer 18 c starts a process of step ST51.

First, the microcomputer 18 c, in step ST51, starts the operation of thecooling device 51.

Then, the microcomputer 18 c, in step ST52, starts the operation in thesecond operation mode. More specifically, the microcomputer 18 cinstructs the information processing unit 11 to switch from theoperating state to a power saving standby state.

Then, the microcomputer 18 c, in step ST53, acquires the detected valueof the temperature sensor 14 from the temperature sensor 14. Then, themicrocomputer 18 c, in step ST54, determines whether or not the detectedvalue acquired in step ST53 is within the reference range.

When the detected value acquired in step ST53 is outside the referencerange (“NO” in step ST54), the microcomputer 18 c returns to the processof step ST53 while causing the cooling device 51 to continue operating,and continuing the operation in the second operation mode (step ST55).

In contrast, when the detected value acquired in step ST53 is within thereference range (“YES” in step ST54), the microcomputer 18 c ends theoperation of the cooling device 51 (step ST56) and performs the firstoperation mode (step ST57). Concretely, for example, the microcomputer18 c advances to the process of step ST23 shown in FIG. 3C.

Next, operations of the standby state maintaining device 100 c will beexplained by reference to a flowchart of FIG. 12, focusing on anoperation of the microcomputer 18 c in the above-mentioned secondconcrete example. In an initial state, the starting switch 3 is in theon state, the power supply unit 12 supplies power to the informationprocessing unit 11 by using the power supplied from the vehicle battery2, and the information processing unit 11 is in the operating state.Further, the secondary battery 13 is in the state in which a charge iscompleted.

More specifically, the electric connection in the switching circuit 15between the vehicle battery 2 and the power supply unit 12 is in the onstate, the electric connection between the secondary battery 13 and thepower supply unit 12 is in the off state, and the electric connectionbetween the vehicle battery 2 and the secondary battery 13 is in the offstate. Further, the switching element 17 is in the off state. When thestarting switch 3 is switched from the on state to the off state, themicrocomputer 18 c starts a process of step ST61.

First, the microcomputer 18 c, in step ST61, starts the operation of thecooling device 51.

Then, the microcomputer 18 c, in step ST62, starts the operation in thesecond operation mode. More specifically, the microcomputer 18 cinstructs the information processing unit 11 to switch from theoperating state to the power saving standby state.

Then, the microcomputer 18 c, in step ST63, calculates the time whichhas elapsed since the starting switch 3 has been switched off. Then, themicrocomputer 18 c, in step ST64, compares the elapsed time calculatedin step ST63 with the third reference time.

When the elapsed time calculated in step ST63 is equal to or less thanthe third reference time (“NO” in step ST63), the microcomputer 18 creturns to the process of step ST63 while causing the cooling device 51to continue operating, and continuing the operation in the secondoperation mode (step ST65).

In contrast, when the elapsed time calculated in step ST63 exceeds thethird reference time (“YES” in step ST64), the microcomputer 18 c endsthe operation of the cooling device 51 (step ST66), and performs thefirst operation mode (step ST67). Concretely, for example, themicrocomputer 18 c advances to the process of step ST23 shown in FIG.3C.

Next, operations of the standby state maintaining device 100 c will beexplained by reference to a flowchart of FIG. 13, focusing on anoperation of the microcomputer 18 c in the above-mentioned thirdconcrete example. In an initial state, the starting switch 3 is in theon state, the power supply unit 12 supplies power to the informationprocessing unit 11 by using the power supplied from the vehicle battery2, and the information processing unit 11 is in the operating state.Further, the secondary battery 13 is in the state in which a charge iscompleted. When the starting switch 3 is switched from the on state tothe off state, the microcomputer 18 c starts a process of step ST71.

The microcomputer 18 c, in step ST71, performs the first operation mode.More specifically, the microcomputer 18 c performs the processing shownin FIG. 3.

Further, in the background to step ST71, the microcomputer 18 c performsa process of causing the cooling device 51 to operate when the detectedvalue of the temperature sensor 14 is greater than the first threshold(step ST72). Concretely, for example, when determining “NO” in step ST2,“NO” in step ST12, or “NO” in step ST24 during the process of step ST71,the microcomputer 18 c starts the operation of the cooling device 51.After that, when determining “YES” in step ST12 or “YES” in step ST24during the process of step ST71 or when the operation in the firstoperation mode is ended, the microcomputer 18 c ends the operation ofthe cooling device 51.

Usually, the temperature of the main body of the secondary battery 13and the ambient temperature of the secondary battery are the highestimmediately after the starting switch 3 is switched off, and, afterthat, gradually decrease with time. Therefore, there is a highprobability that the detected value of the temperature sensor 14 isgreater than the first threshold immediately after the starting switch 3is switched off.

In contrast, the standby state maintaining device 100 c in theabove-mentioned first or second concrete example maintains the powersaving standby state by using the vehicle battery 2 (second operationmode) while cooling the secondary battery 13, immediately after thestarting switch 3 is switched off, and shifts to the first operationmode after the cooling is ended. Further, the standby state maintainingdevice 100 c in the above-mentioned third concrete example cools thesecondary battery 13 while performing the first operation mode. Byvirtue of these cooling operations, the occurrence of a situation inwhich the first operation mode ends without using the secondary battery13 for the maintenance of the power saving standby state can besuppressed while the secondary battery 13 is prevented from beingdischarged in a high temperature environment.

In the above-mentioned second concrete example, the value of the thirdreference time is not limited 30 minutes. The third reference time canbe set to any value in accordance with the capacity of the vehiclebattery 2, the magnitude of the dark current consumed by the informationprocessing unit 11. Further, the third reference time can be the same asthe first reference time, or can be different from the first referencetime.

Further, the timing at which the microcomputer 18 c causes the coolingdevice 51 to operate is not limited to the timing explained in any ofthe above-mentioned first through third concrete examples. Themicrocomputer 18 c can cause the cooling device 51 to operate at anytiming as long as the starting switch 3 is in the off state. However,from the viewpoint of avoiding useless cooling, it is more preferablethat the cooling device 51 is caused to operate at a timing that thereis a high probability that the detected value of the temperature sensor14 is greater than the first threshold, such as a timing immediatelyafter the starting switch 3 is switched off.

Further, the standby state maintaining device 100 c of Embodiment 4 canadopt various variants which are the same as those explained inEmbodiment 1. For example, a part of the processing in the firstoperation mode can be performed by a CPU in the charge and dischargecontrol circuit 16, like in the case of the example shown in FIG. 4. Asan alternative, for example, the secondary battery 13, the temperaturesensor 14 can be provided outside the vehicle-mounted informationapparatus 4, like in the case of the example shown in FIG. 5. In thiscase, the cooling device 51 can be comprised of, for example, a coolingfan provided in a secondary battery module 6.

As mentioned above, in the standby state maintaining device 100 c ofEmbodiment 4, the control unit 19 c causes the cooling device 51 for thesecondary battery 13 to operate in the state in which the startingswitch 3 is off. By virtue of the cooling using the cooling device 51,the occurrence of a situation in which the first operation mode endswithout using the secondary battery 13 for the maintenance of the powersaving standby state can be suppressed.

Further, the control unit 19 c causes the cooling device 51 for thesecondary battery 13 to operate until the detected value falls withinthe reference range after the starting switch 3 has been switched off,and then performs the first operation mode. As a result, the coolingdevice 51 can be caused to operate at a timing that the temperature ofthe main body of the secondary battery 13 and the ambient temperature ofthe secondary battery are high.

Further, the control unit 19 c maintains the power saving standby stateby using the vehicle battery 2 until the detected value falls within thereference range after the starting switch 3 has been switched off. As aresult, the power saving standby state can be maintained also during thecooling, and the secondary battery 13 can be prevented from beingdischarged before the cooling is completed.

As an alternative, the control unit 19 c causes the cooling device 51for the secondary battery 13 to operate until the third reference timeelapses since the starting switch 3 has been switched off, and thenperforms the first operation mode. As a result, the cooling device 51can be caused to operate at a timing that the temperature of the mainbody of the secondary battery 13 and the ambient temperature of thesecondary battery are high.

Further, the control unit 19 c maintains the power saving standby stateby using the vehicle battery 2 until the third reference time elapsessince the starting switch 3 has been switched off. As a result, thepower saving standby state can be maintained also during the cooling,and the secondary battery 13 can be prevented from being dischargedbefore the cooling is ended.

As an alternative, when the detected value is greater than the firstthreshold in the first operation mode, the control unit 19 c causes thecooling device 51 for the secondary battery 13 to operate. As a result,the cooling device 51 can be caused to operate at a timing that thetemperature of the main body of the secondary battery 13 and the ambienttemperature of the secondary battery are high.

It is to be understood that an arbitrary combination of two or more ofthe above-mentioned embodiments can be made, various changes can be madein any component according to any one of the above-mentionedembodiments, and any component according to any one of theabove-mentioned embodiments can be omitted within the scope of theinvention.

INDUSTRIAL APPLICABILITY

The standby state maintaining device of the present invention can beused for the maintenance of a power saving standby state in thevehicle-mounted information apparatus.

REFERENCE SIGNS LIST

1 vehicle, 2 vehicle battery, 3 starting switch, 4 vehicle-mountedinformation device, 5 display device, 6 secondary battery module, 7 GPSantenna, 11 information processing unit, 12 power supply unit, 13secondary battery, 14 temperature sensor, 15 switching circuit, 16charge and discharge control circuit, 17 switching element, 18, 18 a, 18b, 18 c microcontroller (microcomputer), 19, 19 a, 19 b, 19 c controlunit, 21 processor, 22 first memory, 23 second memory, 31 CPU, 41 GPSreceiver, 51 cooling device, and 100, 100 a, 100 b, 100 c standby statemaintaining device.

The invention claimed is:
 1. A standby state maintaining devicecomprising: a secondary battery provided separately from a vehiclebattery; a temperature sensor for the secondary battery; and acontroller having a first operation mode of, in a state in which astarting switch of a vehicle is off, maintaining a power saving standbystate of a vehicle-mounted information apparatus by selectively usingeither the secondary battery or the vehicle battery in accordance with adetected value of the temperature sensor, wherein in the first operationmode, the controller maintains the power saving standby state by usingthe secondary battery when the detected value is within a referencerange, whereas the controller maintains the power saving standby stateby using the vehicle battery when the detected value is outside thereference range.
 2. The standby state maintaining device according toclaim 1, wherein when the detected value falls outside the referencerange while the power saving standby state is maintained using thesecondary battery in the first operation mode, the controller switches astate of the vehicle-mounted information apparatus from the power savingstandby state using the secondary battery to the power saving standbystate using the vehicle battery.
 3. The standby state maintaining deviceaccording to claim 1, wherein when a charge capacity of the secondarybattery becomes less than a reference capacity while the power savingstandby state is maintained using the secondary battery in the firstoperation mode, the controller ends the power saving standby state. 4.The standby state maintaining device according to claim 1, wherein whenthe detected value falls within the reference range while the powersaving standby state is maintained using the vehicle battery in thefirst operation mode, the controller switches a state of thevehicle-mounted information apparatus from the power saving standbystate using the vehicle battery to the power saving standby state usingthe secondary battery.
 5. The standby state maintaining device accordingto claim 1, wherein when a duration of the power saving standby stateusing the vehicle battery exceeds a reference time while the powersaving standby state is maintained using the vehicle battery in thefirst operation mode, the controller ends the power saving standbystate.
 6. The standby state maintaining device according to claim 1,wherein as the reference range, either a range including values equal toor less than a first threshold, or a range including values equal to orgreater than a second threshold less than the first threshold, and equalto or less than the first threshold is set up.
 7. The standby statemaintaining device according to claim 6, wherein when the detected valueis greater than the first threshold in the first operation mode, thecontroller causes a cooling device for the secondary battery to operate.8. The standby state maintaining device according to claim 1, whereinthe controller has a second operation mode of, in the state in which thestarting switch is off, maintaining the power saving standby state byusing the vehicle battery.
 9. The standby state maintaining deviceaccording to claim 8, wherein the controller performs the secondoperation mode until a reference time elapses since the starting switchhas been switched off, and performs the first operation mode after thereference time elapses.
 10. The standby state maintaining deviceaccording to claim 1, wherein the controller causes a cooling device forthe secondary battery to operate in the state in which the startingswitch is off.
 11. The standby state maintaining device according toclaim 1, wherein the controller causes a cooling device for thesecondary battery to operate until the detected value falls within thereference range after the starting switch has been switched off, andthen performs the first operation mode.
 12. The standby statemaintaining device according to claim 11, wherein the controllermaintains the power saving standby state by using the vehicle batteryuntil the detected value falls within the reference range after thestarting switch has been switched off.
 13. The standby state maintainingdevice according to claim 1, wherein the controller causes a coolingdevice for the secondary battery to operate until a reference timeelapses since the starting switch has been switched off, andsubsequently performs the first operation mode.
 14. The standby statemaintaining device according to claim 13, wherein the controllermaintains the power saving standby state by using the vehicle batteryuntil the third reference time elapses since the starting switch hasbeen switched off.
 15. The standby state maintaining device according toclaim 1, wherein the secondary battery comprises either a lithium ionbattery or a nickel-metal hydride battery.
 16. A standby statemaintaining device comprising: a secondary battery provided separatelyfrom a vehicle battery; a temperature sensor for the secondary battery;and a controller having a first operation mode of, in a state in which astarting switch of a vehicle is off, maintaining a power saving standbystate of a vehicle-mounted information apparatus by selectively usingeither the secondary battery or the vehicle battery in accordance with adetected value of the temperature sensor, wherein the controller has asecond operation mode of, in the state in which the starting switch isoff, maintaining the power saving standby state by using the vehiclebattery, and wherein the controller acquires information showing a typeof a facility corresponding to a position of the vehicle when thestarting switch is switched off, and selectively performs either thefirst operation mode or the second operation mode in accordance with thetype of the facility.
 17. A standby state maintaining device comprising:a secondary battery provided separately from a vehicle battery; atemperature sensor for the secondary battery; and a controller having afirst operation mode of, in a state in which a starting switch of avehicle is off, maintaining a power saving standby state of avehicle-mounted information apparatus by selectively using either thesecondary battery or the vehicle battery in accordance with a detectedvalue of the temperature sensor, and having a second operation mode of,in the state in which the starting switch is off, maintaining the powersaving standby state by using the vehicle battery, wherein thecontroller performs the second operation mode until a reference timeelapses since the starting switch has been switched off and performs thefirst operation mode after the first reference time elapses.